Osteopoikilosis: A rare cause of bone pain.

BACKGROUND
Osteopoikilosis (OPK) is a rare inherited condition of the bones, transmitted as an autosomal dominant trait characterized by numerous hyperostotic areas that tend to localize in periarticular osseous regions. It is usually asymptomatic and is often diagnosed incidentally during x-rays made by other reasons. We present a case of 34-year-old man suffering from polyarthralgia and low back pain.


CASE PRESENTATION
A 34-year-old male patient, smoking 40 packs yearly and alcoholic was referred to our department of rheumatology, complaining of polyarthralgia which started 3 years ago and involving large and small joints. He reported the presence of pelvic pain mostly located at both hip joints and in the two ankles. On radiologic examination, numerous, symmetric, well defined, sclerotic lesions were identified on shoulder, wrist, ankles, pelvis, and on spine. The size of the lesions varied from 2 to 9 millimeters. These spots were located on spongious bone tissue, and in the inner bone cortex located bilaterally in the epiphyses and metaphyses. We concluded the diagnosis of OPK. His mother was found to have the same lesions without any symptoms.


CONCLUSION
OPK may be an isolated finding or associated with other pathologies, e.g. skin manifestations, rheumatic and/or skeletal disorders. The main differential diagnosis is osteoblastic metastasis.

O steopoikilosisis is a sclerosing bony dysplasia of unknown etiology with multiple enostosis. It is a rare inherited benign condition incidentally found on squeletal x rays. It is characterized by an abnormality in bone maturation process and often found incidentally on radiologic examination. An autosomal dominant inheritance has been proposed for OPK. Albers-Schonberg was the first to describe this uncommon sclerosing bone dysplasia in 1915 (1). Incidence in both sexes is identical and it can occur at any age. Pain is not a prominent feature of OPK, but in some patients, pain could be a presenting symptom of the disorder.
The signals of this rare hereditary condition are generally found incidentally on plain radiographs. Sometimes this disorder is associated with other abnormalities such as dacryocystitis, dermatofibrosis lenticularis disseminate, scleroderma, discoid lupus erythematosus, keloids, syndactyly, cleft palate, heart or renal malformations, endocrine disorders, and autoimmune disorders (2)(3)(4). The principal considerations in differential diagnosis in the cases of OPK are mastocytosis, tuberous sclerosis, and mainly osteoblastic metastasis. This case shows the importance to keep OPK in mind in patients with diffuse pain to avoid misdiagnosis and invasive diagnostic procedures.

Case Report
A 34-year-old-male patient, smoking 40 packs yearly and alcoholic was referred to our department of rheumatology, complaining of polyarthralgia which started 3 years ago and involving large and small joints. He reported the presence of pelvic pain mostly located at both hip joints and in the two ankles. His pain was constant, but worsened in long distance walking. The   With these clinical and radiologic findings, we concluded the diagnosis of OPK. Management with nonsteroidal antiinflammatory drugs (NSAIDs) and opioid analgesics resulted in improved pain managment. Currently, he continues to require pain medications to maintain his daily activities. Because of the familial nature of the disease, his family members were also evaluated. His mother was found to have the same lesions without any symptoms while his father, his brother and his sister were lesionfree.

Discussion
OPK, also called osteopathia condensans disseminata, asymptomaic bone dysplasia, a spotted bone disease, is a rare disease. It can be transmitted as autosomal dominant or can be sporadic (5). The overall incidence of OPK has been claimed to be  (2). OPK is normally symmetric, numerous, varies in size from a few millimeters to several centimeters, well-defined, homogeneous, and circular or ovoid. Differential diagnosis in plain radiographs may be with mastocytosis, tuberous sclerosis and, principally, osteoblastic metastasis (9). MRI abnormalities observed in our case are the same as those described in the literature. Each lesion is small and dark on both T1 and T2 weighted images, as it is composed of mature dense bone.
Bone scan findings are usually normal in patients with OPK as they were found in our patient, but reveal slightly increased activity similar to the bone island or enostosis that reflects active osseous remodeling. There is no consensus on literature about the treatment.
Non-steroidal anti-inflammatory drugs (NSAIDs) are often used as an option for the treatment of pain. Analgesics such as acetaminophen and opioids can also be used. Rare active lesions have been treated with bisphosphonate therapy, but the results are controversial (10). Our patient was treated with NSAIDs, and opioid analgesics for pain management.
Differential diagnosis from osteoblastic metastasis must be done before performing invasive diagnostic particularly in symptomatic patients and to prevent false alarm for the patients.
OPK is one of the skeletal "don't touch" lesions. Thus, well-timed follow-up visits of the patients are recommended to survey other conditions which may require treatment.